How can i render only one object but still have the rest affecting it?
You can toggle object visibility at render:



Or play for each object with Cycles settings (here in 2.79):



[EDIT]

You can also render just a portion of the screen (CTRL-B on 2.79, then draw the box around your object) which can work mostly if your object doesn't move much in an animation. 

For batching Cycles settings, I guess a python script would work, but that's above my current paygrade.

You can probably find an easy way to run through the objects list and set cycles_visibility.diffuse, cycles_visibility.camera, etc.